Binocular selection for Bios 317 and Bios 337

You will need your own binoculars for Bios 317, Animal Behavior Laboratory, or Bios 337, Bird Field Biology. These must be medium or high quality. They must be completely waterproof and fog proof and say so on them. For Bios 317 or Bios 337, either 8x or 10x will be fine.

The exit hole diameter is what determines light gathering capability, and must be at least 40. This means the binoculars you are most likely to get will be 8 x 42 or 10 x 42. The exit diameter can also be 50 but these tend to be heavy. If you might also use them for watching butterflies (ecology lab, for example), then close focusing is a concern. Your binoculars must be of a decent quality, and so will cost at least $115 before shipping from Eagle Optics. You do not have to get them from this source.

If you are in doubt as to whether a pair of binoculars you already have is adequate, please email me with a full description (

If you are unwilling or unable to purchase binoculars for either of these courses, please drop the course and find another course. The cost of binoculars is not more than many textbooks, and you will have them for your future bird studies.


Summary of binocular requirements:

  • Magnification: 8x or 10x
  • Exit hole dimension: 40 or greater
  • Weatherproofing: Waterproof/Nitrogen purged
  • Close focus: desirable under 12 feet

Possible source:


Suggested binoculars (either the 8 x 42 or the 10 x 42):

  • Nikon Monarch 8 x 42 $290
  • Bushnell Natureview 10 x 42  $125
  • Bushnell Legend 8 x 42 $115
  • Bushell Excursion 10 x 42 $165
  • Pentax PCF WP 11 8 x 40 $149
  • Eagle Optics Denali 10 x 42 $130
  • Stokes Talon 10 x 42 $209 (5 feet close focus!)